Approach to a patient with cardiac amyloidosis

Need for Early Recognition of Amyloidosis in Cases of Unexplained Heart Failure: A Case Report

Amyloidosis is a plasma cell dyscrasia that leads to the excessive production and deposition of mutant protein fragments in various organs. Cardiac amyloidosis is often implicated in two main subtypes: transthyretin (ATTR) and light chain (AL). While both subtypes increase the risk of restrictive cardiomyopathy, cardiogenic shock, and arrhythmias, poorer outcomes are seen in those with cardiac infiltration secondary to AL amyloidosis. Prognosis depends on the timing of diagnosis and the extent of the disease burden prior to recognition and treatment. The following case report describes a young patient who was admitted to the intensive care unit (ICU) for concerns of decompensated heart failure of unknown etiology, later determined to be due to amyloidosis. We describe her clinical course prior to and during hospital admission, along with the proposed physiologic factors that may have contributed to her poor outcome.

Assessment of cardiac amyloidosis with 99mTc-pyrophosphate (PYP) quantitative SPECT

Background

^99mTc-PYP scintigraphy provides differential diagnosis of ATTR cardiomyopathy (ATTR-CM) from light chain cardiac amyloidosis and other myocardial disorders without biopsy. This study was aimed to assess the diagnostic feasibility and the operator reproducibility of ^99mTc-PYP quantitative SPECT.

Method

Thirty-seven consecutive patients who underwent a ^99mTc-PYP thorax planar scan followed by SPECT and CT scans to diagnose suspected ATTR-CM were enrolled. For the quantitative SPECT, phantom studies were initially performed to determine the image conversion factor (ICF) and partial volume correction (PVC) factor to recover ^99mTc-PYP activity concentration in the myocardium for calculating the standardized uptake value (SUV) (unit: g/ml). SUV_max was compared among groups of ATTR-CM, AL cardiac amyloidosis, and other pathogens (others) and among categories of Perugini visual scores (grades 0–3). The intra- and inter-operator reproducibility of quantitative SPECT was verified, and the corresponded repeatability coefficient (RPC) was calculated.

Results

The ICF was 79,327 Bq/ml to convert count rate in pixel to ^99mTc activity concentration. PVC factor as a function of the measured activity concentration ratio in the myocardium and blood-pool was [y = 1.424 × (1 − exp(− 0.759 × x)) + 0.104]. SUV_max of ATTR-CM (7.50 ± 2.68) was significantly higher than those of AL (1.96 ± 0.35) and others (2.00 ± 0.74) (all p < 0.05). SUV_max of grade 3 (8.95 ± 1.89) and grade 2 (4.71 ± 0.23) were also significantly higher than those of grade 1 (1.92 ± 0.31) and grade 0 (1.59 ± 0.39) (all p < 0.05). Correlation coefficient (R²) of SUV_max reached 0.966 to 0.978 with only small systematic difference (intra = − 0.14; inter = − 0.23) between two repeated measurements. Intra- and inter-operator RPCs were 0.688 and 0.877.

Conclusions

^99mTc-PYP quantitative SPECT integrated with adjustable PVC factors is feasible to quantitatively and objectively assess the burden of cardiac amyloidosis for diagnosis of ATTR-CM.

Cardiac amyloidosis presenting with recurrent ischaemic strokes

A 72-year-old man presented to our service with sudden onset right-sided weakness, aphasia and gaze palsy with diplopia. CT angiogram demonstrated an acute thrombotic occlusion of the distal basilar artery, a basilar infarct and the patient underwent successful thrombectomy. ECG and telemetry demonstrated slow atrial fibrillation (AF). His transthoracic echocardiogram (TTE) showed a reduced ejection fraction of 25% with global hypo-kinesis, a dilated left ventricle (LV) and LV hypertrophy (LVH). Repeat TTE appeared suspicious for an infiltrative cardiomyopathy with LVH and a speckled appearance to the myocardium. Approximately 10 months later, he suffered another ischaemic stroke post-elective cardioversion for AF while on anticoagulation. Cardiac MRI demonstrated areas of delayed gadolinium enhancement consistent with amyloidosis. Fat pad biopsy was positive for amyloidosis. Our patient has made an excellent recovery from the ischaemic strokes and is being managed in our heart failure clinic.